Materials Research Activities

Flemming Besenbacher intervew summary

Flemming Besenbacher

Summary of interview conducted on 14. september 2001 at Aarhus Universitet, by Arne Hessenbruch

  1. Early history of surface science
    • 1960s: The US space program boosted surface science in the 1960s by developing oil-free ion pumps and a new ultra-high vacuum technology based on stainless steel chambers, replacing the older glass chambers and mercury pumps. This greatly facilitated the use of a host of sensitive measurement techniques, especially low-energy electron diffraction (LEED) and Auger spectroscopy. As a result, surface science expanded exponentially in the 1970s and '80s.
    • 1980s: The arrival of the Scanning Tunneling Microscope improved not just the resolution to the atomic level, but it also enabled temporal measurements illustrating dynamic effects on the surface. It directly eliminated some theories of surface phenomena and has helped to build up a new conceptual framework for surface science. Prior to the advent of STM, LEED studies dominated surface science conferences; now they have become a small minority.
  2. The beginnings of STM research at Aarhus University (1986-1989)
    • Besenbacher and Ivan Stensgaard had a background in metal surface analysis using ion scattering. In 1986, the use of laser technology seemed unsatisfactory because it yielded only integral information about diffusion on surfaces, whereas the steadily improving STM promised atomic resolution and local information about diffusion. Besenbacher aimed early for information about dynamics of surface phenomena.
    • Resources drawn upon included a well-staffed in-house workshop, funding for both research time and equipment, materials loaned from locally available apparatus (e.g. piezo elements used to direct laser mirrors), and publications (especially Binnig & Rohrer's). Building an STM for ambient use turned out to be quite straightforward.
    • The group then turned to the more challenging task of building one for use in UHV. Here different materials were required, partly because the chamber needs to be baked out before use. Resources for this UHV-STM included an idea for an inchworm motor by Burleigh Instruments. The UHV-STM was tested on the Si 7x7 reconstruction the atomic resolution image of which had been established by September 1989 as a yardstick (Besenbacher's group digressed into semiconductors in this period due to Klaus Mortensen, a post-doc who had spent a year with Gene Golovchenko at Harvard).
    • Outside contacts included Golovchenko, Jürgen Behm, and two students at the Danish Technical University (who in turn had connections to Chalmers University in Gothenburg, Sweden, and Kim Carneiro at the Danish Institute for Fundamental Metrology).
  3. Development of STM theory and difficulties of interpretation
    • STM images result from a convolution of the electronic and geometric surface structure with that of the tip. STM theory utilizes first-order perturbation theory. The interpretation of STM images requires both understanding of the theory and experience, particularly because the tip structure might change during the measurement. Measuring requires patience because the desirable tip structure might suddenly come into being.
    • The development of STM theory has depended heavily on the improvement in computer capacity. The conceptual apparatus of the tunneling theory has changed little: perturbation theory applied to the Hamiltonian with the the tip approximated as an s-wave. The theory for the calculation of surface electronic structure has become known as density function theory.
    • Tip preparation still difficult making replication difficult too.
  4. Center for Atomic-scale Materials Physics (1993-)
    • CAMP was started in 1993 with funding from Danmarks Grundforskningsfond, a funding program fostering a few "elite" research centers. This enabled the gathering of a critical mass of researchers, including many on the PhD and post-doc level. Elite funding was an innovation within Danish research traditions by the centre-right government of Poul Schlüter and, despite its initial opposition, the social democratic government (1992-2001) warmed to it.
    • Close collaboration between a theoretical group at Denmark's Technical University and Besenbacher's experimental one at the University of Aarhus turned out fruitful. The close personal relationship between the two center heads (Jens Nørskov and Besenbacher) mattered greatly. To this day they communicate several times daily. Mutual enrichment has been exemplary, and other centers have modeled themselves on CAMP.
    • One of CAMP's main achievements has been films of movement on metal surfaces in real time. Another has been the design of catalyst surfaces with desirable properties.
    • CAMP has analysed the surface activity of a catalyst used in "steam reforming" for hydrogen production. Scanning probe microscopy methods can be used to design catalysts with desirable qualities. There is a collaboration with the company of Haldor Topsøe, an important supplier of catalysts for ammonium synthesis. This involves contacts, shared research, and Topsøe funding a post-doc position.
    • Linear model (from pure science to application) no longer applicable. Long-term government funding (e.g. 20 years) still desirable, but the separation of institutions doing separate research on pure and applied science non-sensical. Research in the style of Pasteur (basic but simultaneously with a keen eye to application - the reference is to Donald E. Stokes, Pasteur's Quadrant - Basic Science and Technological Innovation, Washington, D.C.: Brookings Institute Press, 1997) is feasible, and CAMP's form of research resembles that of Pasteur. There has been a general shift away from thinking in terms of pure and applied. Funding by private companies is no longer seen as suspect and the next generation is barely aware that such funding used to be scorned.
  5. New projects: biocompatibility and fuel cells
    • Just as it is important for companies to diversify (as the case of Lego reveals), so scientific centres should too. When Hans Jørgen Pedersen, a research director at Danfoss and a member of the faculty board) suggested investigating the possible contributions of scanning probe microscopy (SPM) to biocompatibility research, Besenbacher jumped at the opportunity.
    • It was possible to raise money earmarked for interdisciplinary research and with it to employ two post-docs and a couple of students.
    • New skills have to be developed. Biocompatibility requires investigations of the liquid-solid interface which is in many ways different from research on solid-vacuum interfaces. But the core skills acquired over years with SPM will help substantially nonetheless.
  6. A Danish equivalent of the National Nanotechnology Initiative?
    • Activities are afoot within Danish government ministries to earmark a part of the budget for a Danish equivalent of the National Nanotechnology Initiative. [However, routine budget negotiations were disrupted by November 2001's elections resulting in a change in government from social democrats to a centre-right coalition.]
  7. Patents
    • CAMP has not been in the habit of taking out patents, but there is no reason why this should not change, especially with collaboration on biocompatibility. Colleagues in molecular biology already have much experience with patents. Aarhus University does not put pressure on researchers to apply for patents, though.
This page was last updated on 8 February 2004 by Arne Hessenbruch